Putting laptop LCDs to use with an FPGA

We’re always impressed with the number of laptop displays we’re able to pick out of the trash. Most of the time the computer is borked beyond repair so we end up with a lot of functional but unusable LCD panels. As a service to us all, [EiNSTeiN_] figured out how to control an LCD panel using a cheap homebrew FPGA board.

LCD panels don’t use a simple protocol like VGA for turning pixels on and off. Instead, the very high-speed LVDS is used. LVDS is beyond the capabilities of simple microprocessors, so [EiNSTeiN_] built himself a clone of an XuLA FPGA prototyping board and set to work. After figuring out the signal lines to the panel, [EiNSTeiN_] pored over the timing diagrams for the LVDS controller and the LCD panel. From the data sheets, he figured out data is usually sent to the panel at about 500 MHz. The homebrew FPGA board couldn’t manage that speed so [EiNSTeiN_] cut the FPGA clock in half.

While LCD’s 60 fps refresh rate was reduced to 30 fps, [EiNSTeiN_] says there’s only a little flicker. Not bad for something that could have easily been trashed.

You can run those LCDs at full speed without any problems, you just need to either
– bypass LVDS receiver chip on the panel, its the first IC after the connector.
– use LVDS driver (can be salvaged from old GFX card/laptop for free)

Please elaborate, extremely relevant to my interests. Seriously, has ANYONE not been shot down by the LVDS protocol? If they’d used aa simpler protocol to interface, I’d have my house lit up like Akihibara.

Using the LVDS bus has the advantage of reducing noise and requiring only 8 wires instead of 21. Also, in the case of this panel the ICs are on the wrong side of the PCB so they are not directly accessible, I would be afraid to damage the flex cables running on the edge of the PCB. Those are usually marked “DO NOT TOUCH” in bold red letters, and I heard they are really easy to damage ;)

You tell them the panel resolution and they will program it for you, or you can buy the programmer youtself (2nd link above). Kit includes LCD controller board, LVDS and other cables, LCD keypad, backlight inverter (1-lamp, 2-lamp,or 4-lamp depending on specified preprogrammed LCD panel).

Nice deal for under $33 shipped. Expedited shipping available (from China). Power cube, VGA and DVI cables available (cheap).

Combine it with a frame buffer made using DRAM and you have a very nice display for those microcontroller projects that doesn’t cost an arm and a leg (or tons of CPU cycles). The DRAM will not need refresh and as an added bonus you get a lot more than the 512KB-2MB of the recent projects. Has anyone designed a shield for this? Preferably using a SODIMM?

What an ignorant, uneducated statement. Differential signaling is well within the capabilities of any micro. TakeSingle input, single output. Have you ever heard of RS422? RS485? These differential signaling methods have been around forever.

On a sidenote, the information being sent is only on the rising edge of the clock.
So the information could probably be sent on the falling edge as well, in order to send more commands to the screen.
That’s a future solution I’ve already suggested to him.

Oh yeah, duh. There’s LVDS drivers with builtin frame buffers or DRAM interfaces. I was just hoping that there was some kind of way of recycling those old SDRAMs I have and 256MB sounds like a great addon to any kind of analysis tools. Imagine a bus spy using that for automobiles or an oscilloscope, for example.

We could desolder some chipsets from dead laptop boards? And somehow get Intel to tell us how to program them using anything not made by Intel? LOL, that’s a little bit beyond my skills at the moment. A ‘little’ meaning years.